The invention relates to a module carrier for battery cells, and to a method for producing the module carrier, and to a battery module, a battery pack, a battery and a battery system. The invention furthermore relates to a vehicle, in particular a motor vehicle, such as an electric motor vehicle or hybrid vehicle, with the module carrier, the battery module, the battery or the battery system.
It is foreseeable that both in the case of stationary applications, for example in wind power installations, and in the case of mobile applications, for example in the case of electric motor vehicles (electric vehicles, EV) or hybrid vehicles (hybrid electric vehicles, HEV), use will increasingly be made of novel battery systems, for example with lithium-ion storage batteries or nickel-metal hybrid storage batteries, as rechargeable energy accumulators.
The battery systems have to meet very stringent requirements with regard to the useable energy content, the charging/discharging efficiency, the reliability, the service life and the undesirable loss in capacity due to frequent partial discharging.
A battery system comprises a multiplicity of battery cells. The battery cells heat up during the charging and discharging because of the internal resistance of their cells and the electrochemical processes taking place. The battery cells can be connected in series, in order to increase the electric voltage, and/or can be connected in parallel, in order to increase the maximum electric current. The battery cells can be combined here to form battery units or battery modules. For example, three to twelve battery cells can be combined in a battery module. The battery module holds the battery cells and absorbs mechanical stresses, and therefore the battery module protects the battery cells against damage. Furthermore, the battery module realizes a mechanical bracing of the battery cells and provides electric insulation. In addition, the battery module can serve for controlling the temperature of the battery cells. The battery modules can be combined to form a battery pack. In the event of use for driving vehicles, it is possible for, for example, approximately 100 battery cells to be connected in series or in parallel (as a traction battery). In the case of a high voltage battery system, the total voltage can therefore be, for example, 450 V or even 600 V.
The reliable temperature range for operating the battery cells is typically between −30° C. and +70° C., preferably between +5° C. and +35° C. The performance of the battery cells can decrease significantly in the lower range of the operating temperature. At temperatures of below approximately 0° C., the internal resistance of the battery cells increases significantly, and the performance and the efficiency of the battery cells decrease continuously as temperatures fall further. In this case, irreversible damage to the battery cells may also occur. Even if the operating temperature is exceeded, the performance of the battery cells can decrease significantly. At temperatures over approximately 40° C., the service life of the battery cells is reduced. In this case, irreversible damage to the battery cells can likewise occur. Furthermore, the reliable temperature difference (temperature gradient) for the operation of the battery cells in a battery cell and/or within a battery module or a battery is typically between 5 Kelvin and 10 Kelvin. At greater temperature differences, various regions of a battery cell or various battery cells of a battery module or of a battery can be subjected to different loadings or can even be (partially) overloaded and/or damaged. Furthermore, because of temperature differences and/or temperature changes, there is a risk of condensation water forming in the battery. The damage can lead to accelerated ageing of the battery cells or to thermal runaway of the battery cells, which constitutes a risk for people and the environment.
In a hybrid drive train of a vehicle, Li-ion high performance battery cells are operated with very high dynamics. During brief peak loadings, which arise, for example, due to recuperation of braking energy during braking or boost support during acceleration, the battery cells have to absorb a high power within a very short time (during charging) or dispense a high power in a very short time (during discharging). On account of the internal resistance of the battery cells, these short peak loadings lead to a significant heating of the battery cells. The efficiency of the battery cells during charging and discharging is very high (approximately 95%); nevertheless, the waste heat which arises in the process is not negligible. At a traction power of, for example, 60 KW, a loss of 5% results in a loss of power of 3 KW. Furthermore, for example in the summer months or in warmer regions, external temperatures which may be 40° C. and more may lie outside the permissible temperature range, and therefore, without cooling, the battery cells cannot achieve a service life of, for example, ten years.
In order to ensure the reliability, functioning and service life of the battery module or battery system, it is therefore required to operate the battery cells within the predetermined temperature range. Firstly, as described above, during the operation of the battery cells, heat which has to be removed in order to avoid the battery cells heating up beyond the critical maximum temperature is produced. Secondly, at low temperatures, the battery cells may have to be heated up to a minimum temperature. In order to maintain the predetermined temperature range, the battery module or battery system is temperature-controlled, i.e. cooled or heated according to requirements.
For this purpose, the battery module or battery system can comprise a fluid, for example a liquid, such as alcohol, for example propane-1,2,3-triol (glycerol, glycerine), oil or water or a liquid mixture, as temperature control medium, for example a coolant in a temperature control medium circuit.
The cooling of the battery cells can be achieved, for example, by cooling plates on which the battery cells are mounted. In the cooling plates, either a coolant, such as cooling water (air/heat radiator) or a refrigerant, which is evaporated by the heat (evaporator), absorbs the heat of the battery cells and removes said heat via a radiator to the surroundings or to an air conditioning system (AC). In addition to the cooling plates or the evaporator and the radiator, a cooling system furthermore comprises tubes and/or pipes, for example made of plastic or metal, such as aluminum, for the connection of the cooling plates, the evaporator and/or the radiator.
WO 2012/028927 A2 discloses an electricity accumulator apparatus with a battery pack, comprising a multiplicity of battery cells, a pair of end plates and a multiplicity of clamping bands, wherein the multiplicity of battery cells is arranged between the pair of end plates, and the multiplicity of clamping bands is oriented along the multiplicity of battery cells, on the upper side and lower side thereof, and is fastened in each case to the end plates such that the multiplicity of battery cells is braced between the pair of end plates.
In order to improve the functionality of battery modules and to reduce the costs of the battery modules, the module carrier and the method for producing the module carrier therefore have to be improved.